Work Chair

ABSTRACT

An ergonomic work chair for activities requiring a bent-forward posture has the following features: a supporting cylinder which protrudes from a star base, a supporting column, which is mounted in the supporting cylinder such that it can be displaced in a vertical cylinder axis, for a base plate with a seat which is fixed on the base plate, a base arm which is fitted to the supporting column or to the base plate, and a pivoting arm, which is mounted on the base arm such that it can be rotated out of the seat region about a vertical axis, having a chest rest and side arm rests, and a support which has a star rest and is hinge-connected to the base plate via a lever mechanism which has fulcrums such that pressing down on the seat causes the star rest to move in the direction of the chest rest.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an ergonomic work chair for the performance of activities in bent-forward posture.

PRIOR ART

In manual activities which are practiced in seated position with slightly bent-forward posture, such as, for example, in dentistry, the musculature in the small of the back—the sacro spinalis—is permanently tensed in order to keep the spinal column straight and absorb the torque upon the backbone. This leads to an increasing fatigue of the musculature, resulting in painful muscular strains (for example lumbago). Furthermore, declining muscle strength of the sacro spinalis can no longer hold the spinal column upright, with the result that this deviates rearward and passes into the so-called lordosis posture. This produces a permanent overstraining of the lower vertebrae and causes the chronic lower back pains which are widespread in our civilization.

In a chair disclosed in EP-B-0 672 370, the lumbar rest is connected to the seat surface by a mechanism on the base of a parallelogram. A forward or rearward body movement performed by the sitting person leads to an oppositely directed movement of the lumbar rest.

An orthopedic work chair known from DE-A-44 16 964 has a rest disposed on a U-shaped supporting bracket. The seat surface is mounted rotatably by 180° on a ball bearing mounted swivel plate. The rest serves in a work position to support the chest and in a relax position to support the back. The rotatable seat surface allows a change to be made between the work and relax positions without altering the seat position.

JP-A-2004/049816 discloses a work chair having a chest support disposed on a laterally upward-projecting arm. A rotatable seat surface allows dismounting and standing up unimpeded by the chest support arrangement.

From EP-B-1 275 349, an arrangement with arm supports, which can be detachably fastened to a dentist's chair, is known.

REPRESENTATION OF THE INVENTION

The object of the invention is to provide an ergonomic work chair of the type stated in the introduction, which also allows lengthy working in a bent-forward posture without overstraining of the dorsal musculature.

The object is achieved according to the invention, according to FIG. 1, by a work chair comprising a supporting cylinder projecting upward from a star base, a supporting column for a base plate with a seat secured on the base plate, which supporting column is mounted in the supporting cylinder displaceably in a vertical cylinder axis, a base arm, which is fitted to the supporting column or to the base plate, and a swivel arm, which has a chest rest and lateral arm rests and is mounted on the base arm such that it is rotatable out of the seat region about a vertical axis, and a bracket, which has a lumbar rest and is articulately attached to the base plate, via a lever mechanism having pivot points, such that pressing down the seat causes the lumbar rest to move in the direction of the chest rest.

Advantageous refinements of the invention are the subject of dependent claims.

BRIEF DESCRIPTION OF THE DRAWING

Further advantages, features and details of the invention emerge from the following description of illustrative embodiments and on the basis of the drawing; this shows schematically in

FIG. 1 the side view of a work chair in usage setting, having a first embodiment of a lever mechanism for setting the angular position of the lumbar rest;

FIG. 2 the top view of the work chair of FIG. 1;

FIG. 3 the front view of the work chair of FIG. 1 without lumbar rest;

FIG. 4 a longitudinal section through a first detail of FIG. 3,

FIG. 5 a longitudinal section through a second detail of FIG. 3,

FIG. 6 an oblique view of a third detail of FIG. 3;

FIG. 7 the side view of a work chair without chest rest, having a second embodiment of a lever mechanism for setting the angular position of the lumbar rest;

FIG. 8 the side view of a work chair without chest rest, having a lever mechanism in accordance with FIG. 7 with an additional adjustment facility for the angular position of the lumbar rest;

FIG. 9 the side view of a work chair without chest rest, having a third embodiment of a lever mechanism for setting the angular position of the lumbar rest;

FIG. 10 the side view of a work chair without chest rest, having a third embodiment of a lever mechanism for setting the angular position of the lumbar rest;

FIG. 11 the front view of a variant of the work chair without chest rest, having an additional lumbar rest;

FIG. 12 the partially sectioned side view of a detail for adjusting the height and angular position of the chest rest.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A work chair 10 represented in FIG. 1 consists in its basic structure of a standard star base 12, which has five radial arms 14 arranged in a star shape and having casters 16, and a supporting cylinder 18, which projects vertically upward from the star base 12 and has a supporting column 20 that is mounted on a spring element 22 such that it is displaceable rotatably within said supporting cylinder and slidingly in the direction of the supporting cylinder axis z. That end of the supporting column 20 which lies remote from the star base 12 is connected by a base plate 24 to a seat 26.

A bracket 28 having a lumbar rest 30 fitted thereto is secured to the rear side of the seat 26 pivotably about a horizontal rotation axis 32. The rotation axis 32 divides the bracket 28 into an angled-off long bracket arm 34, having the lumbar rest 30, and into a short bracket arm 36, the free end of which is connected by a compression spring element 38 to a sliding ring 39 that is disposed on the supporting cylinder 18 concentrically to the supporting column 20 and is mounted such that it is freely rotatable about the cylinder axis z.

To the supporting column 20, a base arm 40 is fastened beneath the base plate 24 by a first base arm part 42, which runs horizontally outward, is pivotable about the cylinder axis z and is lockable in any pivot setting. A second base arm part 44 projects vertically upward from that end of the first base arm part 42 which is remote from the supporting column 20. A chest rest 48 and two arm rests 50 are fitted to a swivel arm 46 mounted on the vertically upward projecting second base arm part 44 rotatably about a vertical axis z′ lying parallel to the cylinder axis z.

As can be seen from FIG. 1, the design of the front support afforded to the chest of a person sitting on the work chair 10 by the chest rest 48 and of the rear support afforded to the small of the back by the lumbar rest 30 results in the upper body being clamped in place between the chest rest 48 and the lumbar rest 30. In addition, the arms are relieved of load by resting upon the arm rests 50.

Through the combination of these three measures, health-damaging loads which are generated when sitting with slightly bent-forward posture while practicing manual activities are largely eliminated as follows:

-   -   The weight of the bent-forward upper body is supported on the         chair by the chest rest 48, so that the sacro spinalis no longer         has to hold the upper body.     -   The small of the back is pressed synchronously with said support         by means of the chest rest 48 by a lumbar or lumbar rest 30, via         an adjustable spring force, forward in the direction of the         upper body or chest rest 48, so that the spinal column cannot         deflect rearward into the lordosis posture.     -   The arms of the sitting person, who is generally also holding         tools or work items in their hands, can be supported on the         forward-directed arm rests 50.

As a result of said measures, the musculature of the dorsal section is optimally relieved of the forward-acting torque.

In order that it is possible to sit on the seat 26 in the usual manner, the swivel arm 46, to which the chest rest 48 and the arm rests 50 are fastened, is mounted on the vertically upward projecting second base arm part 44 (FIG. 2 and 3). Following the release of a locking mechanism, the swivel arm 46 can be swung away laterally in a horizontal plane in the direction of the arrow. The first base arm part 42 is fastened to the supporting column 20, or to the adjoining base plate 24, by a clamp-type mounting 52 having a clamping screw 54. Through an appropriate turning of the clamping screw 54, the clamp-type mounting 52 is able to be released and re-fixed. In this way, the base arm 40 can be pivoted on the supporting column 20 about the cylinder axis z and altered in its horizontal angular position.

The angular setting of the base arm 40 and of the first base arm part 42 relative to the seat direction x lies roughly between 45° and 60°, so that the freedom of movement of the legs of a person sitting on the work chair 10 is not restricted by the base arm 40, while a torsional moment which is as low as possible acts upon the linkage consisting of base arm 40 and swivel arm 46.

The angular setting between the base arm 40 and the swivel arm 46 in the locking position can be adapted to the body size of the person sitting in the work chair 10, as is explained in greater detail below with reference to FIG. 4.

Within the tubular second base arm part 44, a tubular hinge 56 for the rotatable mounting of the likewise tubular swivel arm 46 is arranged. The hinge 56 is fixed by a clamping force acting radially against the inner wall of the second base arm part 44. To this end, the lower part of the hinge 56, which is disposed in the second base arm part 44, is provided with a longitudinal slit 58. A first screw nut 60 is fixed to the inner wall of the hinge 56, for example, with a welding spot 61. A threaded rod 64 engaging in the thread of the first screw nut 60 is led in the axial direction z′ out of the second base arm part 44 and is provided outside the base arm 40 with a handwheel 62. To the threaded rod 64, a second screw nut 66 is fixed beneath the first screw nut 60 such that it is non-displaceable on the threaded rod 64. Between the two screw nuts 60, 66 there is arranged an expanding ring 68. Through rotation of the handwheel 62 and thus of the threaded rod 64, the expanding ring 68 is applied to the first screw nut 60 and, upon continued rotation of the handwheel 62, is compressed by the second screw nut 66 such that it expands toward the inner wall of the tubular hinge 56 provided with a longitudinal slit 58. The hinge 56 is hereupon radially expanded owing to the longitudinal slit 58 and is braced against the inner wall of the second base arm part 44. In this way, the angular setting of the locked swivel arm 46 relative to the base arm 40 is altered by releasing the clamping joint between the hinge 56 and the second base arm part 44, and the base arm 40 can be fixed in the new angular setting of the locked swivel arm 46 by renewed clamping of the hinge 56 in the second base arm part 44.

FIG. 5 shows a possible locking of the swivel arm 46 on the base arm 40. A bolt 70 passes through a first bore 72 in the wall of the tubular hinge 56 and through a locking bore 74 in the wall of the tubular swivel arm 46 mounted rotatably on the hinge 56. The swivel arm 46 is thereby fixed in its locking position. A strip-shaped leaf spring 76 disposed inside the tubular hinge 56 is fixedly connected on one side to the bolt 70 and on the opposite side bears against the inner wall of the tubular hinge 56. The bolt 70 through the locking bore 74 in the swivel arm 46 is hence forced outward. By use of the thumb, this bolt 70 can be pushed into the locking bore 74 and thus the swivel arm 46 released from its locking position and pivoted horizontally out of the seat region.

With the hability of the swivel arm 46 with chest rest 48 and arm rests 50 to swing away to the side, the work chair 10 can also be used conventionally when no activity is performed with bent-forward posture, the sitting person requires space which is unoccupied to the front, or simply wishes to stand up.

The arm rests 50 are secured by means of a fixable ball joint 82 on a radial arm 80, which latter is adjustably fitted to a clamping sleeve 84 on the swivel arm 46 (FIG. 6). The clamping sleeve 84 can be twisted about the swivel arm 46, the fastening of the radial arm 80 being realized via a swivel joint 83. The clamping sleeve 84 and the radial arm 80 are fixed with a clamping screw 86. As a result of the threefold adjustability, the arm rests 50 can be spatially positioned according to choice.

The chest rest 48 is fitted in a height-adjustable manner by means of a clamping bracket 90 and a clamping screw 92 to a bar 88 (FIG. 6). The bar 88 is provided with a clamping sleeve 94 fastened to the swivel arm 46. The clamping sleeve 94, like the clamping sleeve 84, can be twisted on the swivel arm 46, so that the chest arm 48 can additionally be adjusted in the seat direction x.

The chest rest 48 is configured in a heart shape or is equipped with a rest part 49 supporting the sternum, so that female users of the work chair 10 can lean comfortably against it.

In order to make it easier to sit down and get up, the lumbar rest 30 is designed such that it opens rearward by an angle of about 10° to 20° when the seat 26 is empty (FIG. 7). This is achieved by a lever mechanism with spring force transmission. For the actuation of the lever mechanism, various geometric arrangements are conceivable.

In the arrangement shown in FIG. 7, the seat 26 is fixedly mounted on a base plate 24. On the base plate 24 is located a first pivot point 96, to which the bracket 28 of the lumbar rest 30 is fastened rotatably about a horizontal rotation axis. On the bracket 28 of the lumbar rest 30 there is a second pivot point 98. A third pivot point 100 is located on the sliding ring 39, which is arranged on the supporting cylinder 18 concentrically to the supporting column 20 and is mounted such that it is freely rotatable about the cylinder axis z. Between the pivot point 98 and the pivot point 100 there exists, via the spring element 38, a resiliently elastic joint. If the seat 26 is forced downward by the body weight of the sitting person, the supporting column 20 penetrating into the supporting cylinder 18, the vertical distance between the second pivot point 98 and the third pivot point 100 diminishes. Owing to the non-positive connection, the second pivot point 98 on the bracket 28 of the lumbar rest 30 deflects rearward, and the lumbar rest 30 is moved forward in the seat direction x by a rotation of the bracket 28 about the horizontal rotation axis of the second pivot point 98.

FIG. 8 shows an additional adjustment facility for the angular position of the lumbar rest 30 to compensate for a different body size of the sitting person. The second pivot point 98 disposed on the bracket 28 is no longer fixed, but is located on a slide 104 guided in a slide rail 102. By means of an adjusting screw 106, the position of the second pivot point 98, and thus the lever geometry, is altered.

FIG. 9 shows a configuration in which the seat 26 supported by a spring element 108 intrudes with a column 112 into an intermediate cylinder 110 fastened on the supporting column 20. This configuration allows greater spring deflection depths as the output parameter for the lever mechanism of the lumbar rest 30. Articulately attached to the bracket 28 of the lumbar rest 30 is, at the second pivot point 98, an auxiliary bracket 114 fastened to the intermediate cylinder 110. The first pivot point 96 and the third pivot point 100 are mutually connected by a compression spring element 116. This configuration corresponds to the arrangement of the lever mechanism of FIG. 7.

In the arrangement shown in FIG. 10, the base plate 24 is fitted to the front side of the seat 26 via a swivel joint 118 on an intermediate bracket 120. The seat 26 is supported on the intermediate bracket 120 by a spring element 122. The pivot point 98 of the bracket 28 of the lumbar rest 30 is secured on the rear side of the seat 26 to the intermediate bracket 120. The first pivot point 96 and the third pivot point 100 are mutually connected by the compression spring element 116. The lever mechanism for the deflection of the lumbar rest 30 corresponds to that of the arrangement according to FIG. 9.

The configuration of lumbar rest 30, chest rest 46 and arm rests 50 also allows an additional use of standard arm rests on the sides of the seat.

For comfortable leaning back, the lumbar rest 30 can be bridged with a second lumbar rest 31 which partially encloses it (FIG. 11). The lumbar rest 30 moves, according to the load imposed by the sitting person, through the second lumbar rest 31. The second lumbar rest 31 is fastened to the base plate 24 by a bracket 29.

There are manual activities in which the sitting person must lean further forward. This is the case, for example, in dental treatments in which the treating dentist must get very close to the mouth of the patient. FIG. 12 shows for this purpose a special version of the base arm 40 having the facility for altering the angular setting of the second base arm part 44 and for height-adjusting the swivel arm 46 with chest rest 48 and arm rests 50. The tubular first base arm part 42 is divided into a fixed part 42 a secured to the supporting column 20 and a part 42 b rotatable about the tube axis of the fixed part 42 a. In the fixed part 42 a there is disposed a hinge 43 connected thereto. On the hinge 43 projecting from the first part 42 a, the rotatable part 42 b is slidingly mounted. The dividing point 124 between the two parts 42 a, b is configured in a step shape with interlocking steps.

An adjusting lever 126 is hinge-connected, by two arms 128, 130 forming a bell crank mechanism, to respectively one of the two parts 42 a, b of the first base arm part 42. A first arm 128 is articulately attached directly to the rotatable part 42 b, the second arm 130 to a sliding ring 132 rotatably mounted on the fixed part 42 a. The two points of attachment of the arms 128, 130 to the two parts 42 a, b are mutually connected by a spring element 134 under tensile stress.

By pressing down the adjusting lever 126, the two parts 42 a, b of the first base arm part 42 are drawn apart at the step-shaped dividing point 124 such that the two parts 42 a, b detach from their toothing. By leaning forward and applying force to the chest rest, the sitting person can turn the part 42 b sliding on the hinge 43 and angle the second base arm part 44 forward counter to the force of a restoring spring—in FIG. 12 a torsion spring 136 disposed inside the first base arm part 42. Following the release of the adjusting lever 126, the spring element 134 closes the bell crank, so that the connection of the parts 42 a, b culminates in an altered angular setting. After the sitting person has straightened up again, the torsion spring 136 returns the rotatable part 42 b into the basic setting.

The second base arm part 44 supporting the swivel arm 46 is detachably fastened in a clamp 138 disposed on the free end of the part 42 b, which clamp can be tightened with a clamping screw 140. This arrangement allows a height adjustment of the entire chest link mechanism, whereby the geometry can be adapted to different body sizes. In addition, the angular setting of the second base arm part 44 can be adapted.

REFERENCE SYMBOL LIST p0 10 work chair

-   12 star base -   14 radial arm -   16 casters -   18 supporting cylinder -   20 supporting column -   22 spring element -   24 base plate -   26 seat -   28 bracket -   29 second bracket -   30 lumbar rest -   31 second lumbar rest -   32 rotation axis -   34 long bracket arm -   36 short bracket arm -   38 compression spring element -   39 sliding ring -   40 base arm -   42 first base arm part -   42 a fixed part of 42 -   42 b rotatable part of 42 -   43 hinge -   44 second base arm part -   46 swivel arm -   48 chest rest -   49 narrow chest rest part -   50 arm rests -   52 clamp-type mounting -   54 clamping screw -   56 hinge -   58 longitudinal slit -   60 first screw nut -   61 welding spot -   62 handwheel -   64 threaded rod -   66 second screw nut -   68 expanding ring -   70 bolt -   72 first bore -   74 locking bore -   76 leaf spring -   80 radial arm -   82 ball joint -   83 swivel joint -   84 clamping sleeve -   86 clamping screw -   88 bar -   90 clamping bracket -   92 clamping screw -   94 clamping sleeve -   96 first pivot point -   98 second pivot point -   100 third pivot point -   102 sliding rail -   104 slide -   106 adjusting screw -   108 spring element -   110 intermediate cylinder -   112 column -   114 auxiliary bracket -   116 compression spring element -   118 swivel joint -   120 intermediate bracket -   122 spring element -   124 step-shaped interface -   126 adjusting lever -   128 first arm of a bell crank -   130 second arm of a bell crank -   132 sliding ring -   134 spring element -   136 torsion spring -   138 clamp -   140 clamping screw -   x seat direction -   z supporting cylinder axis -   z′ vertical axis 

1-12. (canceled)
 13. A work chair, comprising a supporting cylinder projecting upward from a star base, a supporting column for a base plate with a seat secured on the base plate, which supporting column is mounted in the supporting cylinder displaceably in a vertical cylinder axis, a base arm, which is fitted to the supporting column or to the base plate, and a swivel arm, which has a chest rest and lateral arm rests and is mounted on the base arm such that it is rotatable out of a region of the seat about a vertical axis, and a bracket, which has a lumbar rest and is articulately attached to the base plate, via a lever mechanism having pivot points, such that pressing down the seat causes the lumbar rest to move in the direction of the chest rest.
 14. The work chair as claimed in claim 13, wherein the base arm is detachably fitted to the supporting column or to the base plate.
 15. The work chair as claimed in claim 13, wherein the swivel arm is mounted on a tubular hinge secured in the base arm, and a resiliently mounted bolt, in a locked usage setting of the swivel arm, passes through a first bore in the hinge and a locking bore in the swivel arm and can be pressed in counter to a spring force to release the locking.
 16. The work chair as claimed in 15, wherein the tubular hinge can be radially expanded toward an inner wall of the base arm by means of an expansion device and forms with the base arm a detachable clamping joint.
 17. The work chair as claimed in claim 13, wherein the chest rest having a narrow rest part is fitted to the swivel arm such that it can be adjusted in height and pivoted in a seat direction.
 18. The work chair as claimed in claim 13, wherein the arm rests are fastened to a radial arm by means of a fixable ball joint, and the radial arm is secured via a swivel joint to a clamping sleeve arranged adjustably on the swivel arm.
 19. The work chair as claimed in claim 13, wherein the bracket is fastened to the base plate at a first pivot point rotatably about a horizontal rotation axis, and a second pivot point on the bracket is connected by a spring element to a third pivot point on a sliding ring, which is disposed on the supporting cylinder concentrically to the supporting column and such that it is freely rotatable about the cylinder axis.
 20. The work chair as claimed in claim 19, wherein the second pivot point on the bracket is disposed, such that it is adjustable in its position, on a slide guided in a slide rail.
 21. The work chair as claimed in claim 13, wherein the seat is mounted via a column in an intermediate cylinder such that it is displaceable in the cylinder axis, the bracket is articulately attached via a second pivot point to an auxiliary bracket fastened to the intermediate cylinder, and a third pivot point on a free end of the bracket is connected by a compression spring element to a first pivot point on the base plate.
 22. The work chair as claimed in claim 13, wherein the base plate is fitted to a front side of the seat via a swivel joint on an intermediate bracket and is supported by a spring element, the bracket is articulately attached via a second pivot point on the rear side of the seat to the intermediate bracket, and a third pivot point on the free end of the bracket is connected by a compression spring element to a first pivot point on the base plate.
 23. The work chair as claimed in claim 13, wherein the lumbar rest is bridged by a second lumbar rest particularly enclosing it and can be moved through this.
 24. The work chair as claimed in claim 13, wherein the base arm has a first base arm part and a second base arm part projecting vertically upward from this and supporting the swivel arm, and the first base arm part is divided into a fixed first part and a rotatable second part, wherein the two parts can be drawn apart at a step-shaped dividing point by means of an adjusting lever and, following rotation of the second part, can be fixed at a preselected tilt setting of the second base arm part. 